1.9 dci 120 low mpg

[Grale]

I bought a 2005 1.9 dci 120 on friday, when i looked at the current mpg on the computer it said only 20 something mpg!! all readings had been zeroed
by the garage i think, possibly even battery removed.

4 days later and 72 miles on the trip, and with carefull driving it has risen to 34 mpg. now does it take time for the true reading to show or could this be a problem?

the car has done 50,000. my clio cup had the same kind of trip computer, but it only took a very short trip to display the correct mpg!!

Thanks

edit: sorry these miles were all done urban driving

[dci120matt]

i have found that its hard to get the mpg up if you know what i mean, the only way i have found to get a semi accurate reading was just before i go on the motorway or another journey that you are a pretty constant speed reset the trip then. then hopefully your mpg will rise then stay at a more believable reading

[terry_mccann]

the longer you leave the BC un-resetted, the more exact your results will be....this is simple arithmetics when calculating averages....and also compare the results to the results you measure when filling the car up and reading the miles off the clock.

here in germany we measure this in Litres per 100 km and my boardcomputer shows half a litre more than what I calculate when filling it.

[nickbell69]

As Terry says the longer you leave it the better an average it will show. Mine is about 48 at the moment.

[Grale]

Ok thaks guys, that makes me feel a bit more confident!

Can i reset just the trip on the miles after i have filled up, or will it also clear the mpg ?

[keeforelli]

hi


if you reset the trip computer/miles/ it resets everything and you go back to zero-

also, as already said on here...if you reset it and do mainly urban miles its very difficult to get the average up, this being the least efficient journey type- it never gets a chance to calculate a high MPG to increase the average which would be when its running at its most fuel efficient..ie on A roads with no braking and accelerating.

get a good long run in there, reset it while your moving to get a high average, say at 60mph, and it will settle down far better.

[Gav]

On my trip, if I hold the reset on what I'll call the first screen, which has total miles and a trip, you reset that first trip. Cycle through fuel used, mpg, range and a second trip wont have been affected, and need another reset (from any of them) to zero them.

Due to the closest Shell stations being the other side of town from where I live, I often fill up and drive through town, but can get the economy back into at least mid 50's by the time I get home, it having been really low when waiting at lights just after a reset.

[terry_mccann]

On my trip, if I hold the reset on what I'll call the first screen, which has total miles and a trip, you reset that first trip. Cycle through fuel used, mpg, range and a second trip wont have been affected, and need another reset (from any of them) to zero them.

Exactly....in mine it's the same.

[Rich B]

I tend to monitor my mpg tank to tank and I've found the best indication of the fuel economy you get from any one tank of fuel is obtained by resetting the mpg when you fill up. I've started doing this becoz I had a tank of fuel from BP which gave me surpringly low mileage yet the mpg reading said 65mpg! Using this practice and subsequently calculating mpg from the litres used to refill shows that the trip computer is accurate to +/- 2mpg. Otherwise - the information it gives is not entirely relevant to the fuel you're actually using! Particularly useful I say given the cost of fuel at the moment. All of the above contributors are quite correct in saying that it will take time for the mpg reading to settle due to the law of averages.

Somebody else posted the following which I use to calculate my 'genuine' mpg:

Number of litres (divided by) 4.546 = Number of Gallons

Distance (miles) traveled (divided by) Number of Gallons = MPG

[Grale]

Distance (miles) traveled (divided by) Number of Gallons = MPG

Well going off my current Miles: 133 and fuel used: 3.7 gallons which the computer tells me.

That works out at 35.9 mpg that's crap!! i got 34mpg in my clio Sport 172 cup 2.0l petrol !!

I'm going to run this tank down, put £20 in the tank and see exactly how many miles i get out of that..

Hopefully it will just be the tc, but i've got a bad feeling it's not :¬(

[Grale]

What speeds were you travelling at? I get about that from a 1.9dci commuting journeys around 2 miles when my average speed is around 19mph.

Journey to work exactly 4.0 miles average speed 30-40mph with probably only 3 or 4 stops in that journey for lights and turning. with no fast accelerating at all.

[Grale]

If I may be so bold, what average speed does your computer say you were doing, its surprising how a a short journey which barely warms the engine up and even just a few stops can reduce your average speed.

I had just thought of that as i posted,it say's 17.5 average speed.

I understand what you are saying about distance and speed, i am just a little dissapointed as my clio was not far behind on mpg (driven harder!)and diesel is more expensive than petrol.

Thanks for your input much appreciated